Color inhomogeneity is an issue in many LED products. Color inhomogeneities arise due to color over position (CoP) and color over angle (CoA) for single LEDs, slightly different color temperatures for products where multiple LEDs are used, different color temperatures for products that can vary in overall color temperature (from warm white to cool white), and completely different colors for products that contain colored LEDs (for instance red, green and blue LEDs).
In present-day LED lamps and LED modules the color issues are solved using diffusers (often in combination with a mixing chamber) or mixing rods. However diffusers cause a lower system efficiency, and mixing rods require relatively large amounts of space.
Another attempt at solving the above-mentioned color issues is described in JP 50-38755 B2 disclosing a LED luminaire comprising a lens arranged over a plurality of LEDs. The lens comprises, seen in a planar view, several radially extending V-grooves provided in an outer surface of the lens such that the lens has an uneven or corrugated surface structure. The uneven or corrugated surface structure is provided in a cross sectional plane being parallel to the optical extraction surface of each of the plurality of LEDs. In addition to insufficient color mixing, this solution, however, necessitates an overly complex lens surface structure and is thus expensive to manufacture.